U.S. patent application number 09/884092 was filed with the patent office on 2002-01-17 for method and circuit for driving electrophoretic display, electrophoretic display and electronic device using same.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Katase, Makoto.
Application Number | 20020005832 09/884092 |
Document ID | / |
Family ID | 27343808 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020005832 |
Kind Code |
A1 |
Katase, Makoto |
January 17, 2002 |
Method and circuit for driving electrophoretic display,
electrophoretic display and electronic device using same
Abstract
A method for driving an active matrix electrophoretic display is
provided. In a resetting period Tr, reset data Drest is supplied to
a data line drive circuit and a reset voltage is applied to each
pixel electrode. Next in a writing period, an image data is
supplied to a data line drive circuit and a gradation voltage is
applied to each pixel electrode. Subsequently a common voltage is
applied to it, in order to take charge which is accumulated between
the electrodes away, applying no electric field to a dispersal
system. Then a displayed image is held.
Inventors: |
Katase, Makoto; (Nagano-ken,
JP) |
Correspondence
Address: |
Oliff & Berridge PLC
P.O. Box 19928
Alexandria
VA
22320
US
|
Assignee: |
SEIKO EPSON CORPORATION
4-1, Nishishinjuku 2-chome, Tokyo
Shinjuku-ku
JP
163-0811
|
Family ID: |
27343808 |
Appl. No.: |
09/884092 |
Filed: |
June 20, 2001 |
Current U.S.
Class: |
345/107 |
Current CPC
Class: |
G09G 2360/18 20130101;
G09G 3/2011 20130101; G09G 2310/027 20130101; G09G 2310/06
20130101; G02F 1/167 20130101; G09G 2310/061 20130101; G09G 3/344
20130101; G09G 2320/0276 20130101; G09G 2310/04 20130101; G09G
2310/0205 20130101; G09G 2300/08 20130101; G09G 2310/062 20130101;
G09G 2330/021 20130101; G09G 2340/16 20130101 |
Class at
Publication: |
345/107 |
International
Class: |
G09G 003/34 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2000 |
JP |
2000-187922 |
Aug 3, 2000 |
JP |
2000-236197 |
Jun 20, 2001 |
JP |
2001-187279 |
Claims
What is claimed is:
1. A display comprising a common electrode, a plurality of pixels
and a plurality of switching elements, with one of each of said
switching elements being assigned to a corresponding one of said
pixels, and each of said pixels comprising: a pixel electrode
connected to one of said switching elements, and provided in spaced
opposing relation to said common electrode; and a dispersal system
comprising a colored fluid in which pigment particles are
suspended, said dispersal system being provided between said common
electrode and one of said pixel electrodes; and the method
comprising: a.) applying a 1st voltage to said common electrode;
b.) applying a 2nd voltage to one of said pixel electrodes via a
corresponding one of said attached switching elements, to generate
an electrostatic field in said dispersal system, to cause said
pigment particles to migrate in the direction of the thus generated
field to a position corresponding to a color gradation desired for
a pixel; and c.) applying said 1st voltage via a corresponding said
switching element to said pixel electrode, to cancel the
electrostatic field and fix said pigment particles in a desired
position.
2. The method of claim 1, wherein a reset voltage corresponding to
a gradation to be displayed is applied to said 2nd electrode to
cause said pigment particles to migrate to an initial position.
3. The method of claim 1, wherein after application of said reset
voltage to said second electrode, a brake voltage is applied to
said second electrode to halt rapidly the movement of said pigment
particles.
4. The method of claim 1, wherein when an image displayed is to be
switched; a differential voltage, which is a difference between a
voltage corresponding to a color gradation displayed previously and
that to be displayed, as a 2nd voltage is applied both before and
after switching said image.
5. A method for driving an electrophoretic display, the display
comprising: a plurality of data lines; a plurality of scanning
lines, each of which intersects said data lines; a common
electrode; a plurality of pixel electrodes, with one of said
plurality of pixel electrodes being provided at one of each of said
intersections of said data lines and said scanning lines, each of
said pixel electrodes being provided in opposing spaced relation to
said common electrode; a plurality of dispersal systems comprising
a colored fluid in which pigment particles are suspended, with each
of said dispersal systems being provided between said common
electrode and one of said pixel electrodes; and a plurality of
switching elements, with one of each of said switching elements
being provided at a corresponding one of each of said intersections
of said data lines and said scanning lines, with an on/off control
terminal being connected to one of said scanning lines passing
through one of said intersections; and with one of said data lines
passing through one of said intersections, being connected to one
of said pixel electrodes provided at each of one said
intersections; and the method comprising: controlling an image
displayed by employing said scanning lines and said data lines,
each of said voltages being applied within a set period of one
scanning field, in which all of said scanning lines are once
scanned; and within a said set period of scanning field; applying a
common voltage to a said pixel electrode; selecting said scanning
lines sequentially; applying a voltage to a selected scanning line,
to turn on all switching elements connected to the said
sequentially selected scanning line; applying a plurality of pixel
voltages to a plurality of said data lines for a set time, to
generate electrostatic fields to cause pigment particles to migrate
to positions corresponding to desired color gradations of an image
displayed; and applying a voltage to said sequentially selected
scanning line, to turn off all of said switching elements connected
to said sequentially selected scanning line.
6. The method of claim 5, comprising: applying said 1.sup.st
voltage during a first period of a scanning field; applying said
reset voltage during a next and different scanning field; applying
each of said voltages alternately; in said first period; applying a
plurality of voltages to said plurality of data lines, to create an
electrostatic field in each of said dispersal systems, to
initialize said pigment particles; and in said next period; when
applying said 1.sup.st voltage, applying a plurality of voltages
for obtaining a desired color gradations corresponding to desired
color gradations to said selected data lines
7. The method of claim 6, when a displayed image is switched;
applying said 1.sup.st voltage and said reset voltage to only those
pixel electrodes corresponding to pixels the color gradation of
which changes following switching of an image displayed.
8. The method of claim 7, further comprising: selecting a plurality
of said scanning lines simultaneously; and applying said reset
voltage to a plurality of said data lines, so that said reset
voltage is applied simultaneously to said plurality of pixel
electrodes to initialize said pigment particles, .
9. The method of claim 5, further comprising: applying a plurality
of brake voltages to said data lines, to create electrostatic
fields, to halt rapidly said pigment particles, after applying said
pixel voltages to said data lines.
10. The method of claim 5, further comprising: applying said reset
voltages during a previous said period of a scanning field;
applying a differential voltage to said pixel electrodes during a
said period; in a said set period for applying said reset voltage;
applying a plurality of voltages to the pixel electrodes, to
initialize the pigment particles; and in said set period for
applying said pixel voltage; applying a differential voltage to the
data lines, which voltage corresponds to a difference between a
voltage corresponding to a color gradation displayed in a previous
voltage applying operation, and a next color gradation to be
displayed.
11. The method of claim 9, further comprising: applying said brake
voltages to said data lines, to create electrostatic fields to halt
rapidly said pigment particles, after applying said pixel voltages
to said data lines.
12. The method for driving an electrophoretic display, the display
comprising: a plurality of data lines; a plurality of scanning
lines, each of which intersects said data lines; a common
electrode; a plurality of pixel electrodes, provided at each
intersection of said data lines and said scanning lines, each of
said pixel electrodes being provided in opposing spaced relation to
said common electrode; a plurality of dispersal systems, comprising
a colored fluid in which pigment particles are suspended, with each
of said dispersal systems being provided between said common
electrode; and a plurality of switching elements, with one of each
of said switching elements being provided at a corresponding one of
each of said intersections of said data lines and said scanning
lines, with an on/off control terminal being connected to one of
said scanning lines passing through one of said intersections; and
with one of said data lines passing through one of said
intersections, being connected to one of said pixel electrodes
provided at each of one said intersections; and the method
comprising: controlling an image displayed by employing said
scanning lines and said data lines, each of said voltages being
applied within a set period of one scanning field, in which all of
said scanning lines are once scanned; and applying a voltage for
resetting said pigment particles in a said first period; applying a
voltage for obtaining a desired color gradation in a said second
period; applying a voltage for holding images displayed in a said
third period; in said first period; applying a common voltage to a
said pixel electrodes; selecting sequentially said scanning lines;
applying a voltage to a said sequentially selected scanning line,
to turn on all switching elements connected to the said
sequentially selected scanning line; applying a plurality of pixel
voltages to a plurality of said data lines for a set time, to
create electrostatic fields, to initialize said pigment particles
in each of said dispersal systems; and applying a voltage to the
scanning line selected, in order to turn off all the switching
elements connected to the relevant scanning lines; and in said
second period; applying said common voltage to said common
electrode; selecting said scanning lines sequentially; applying a
voltage to said sequentially selected scanning lines, to turn on
all of said switching elements connected to said sequentially
selected scanning lines; applying a plurality of voltages to said
data lines; applying a plurality of voltages to said sequentially
selected scanning lines, to turn off all of said switching elements
connected to said sequentially selected scanning lines; and in said
third period; applying the common voltage to the common electrode;
selecting the scanning lines sequentially; applying a voltage to
said sequentially selected scanning lines, to turn on all of said
switching elements connected to the said sequentially selected
scanning lines; applying said common voltage to said data lines
applying said pixel voltages to said sequentially selected scanning
lines, to turn off all the switching elements connected to the said
sequentially selected scanning lines.
13. The method of claim 12, further comprising: applying a
plurality of voltages to said data lines, to create a plurality of
electrostatic fields, to brake said pigment particles during one
scanning field period after said second period, before said third
period.
14. The method of claim 12, further comprising: when a set time
passes after applying to obtain a desired color gradation said
plurality of voltages; applying a voltage for resetting said
pigment particles in a said first period; applying a voltage for
obtaining a desired color gradation in a said second period;
applying a voltage for holding images displayed in a said third
period;
15. A method for driving an electrophoretic display, the display
comprising: a plurality of data lines; a plurality of scanning
lines, each of which intersects said data lines; a common
electrode; a plurality of pixel electrodes, with one of said
plurality of pixel electrodes being provided at one of each of said
intersections of said data lines and said scanning lines, each of
said pixel electrodes being provided in opposing spaced relation to
said common electrode; a plurality of dispersal systems comprising
a colored fluid in which pigment particles are suspended, with each
of said dispersal systems being provided between said common
electrode and one of said pixel electrodes; and a plurality of
switching elements, with one of each of said switching elements
being provided at a corresponding one of each of said intersections
of said data lines and said scanning lines, with an on/off control
terminal being connected to one of said scanning lines passing
through one of said intersections; and with one of said data lines
passing through one of said intersections, being connected to one
of said pixel electrodes provided at each of one said
intersections; and the method comprising: controlling an image
displayed by employing said scanning lines and said data lines,
each of said voltages being applied within a set period of one
scanning field, in which all of said scanning lines are once
scanned; and within a said set period of scanning field; applying a
voltage for resetting said pigment particles in a said first
period; applying a voltage for obtaining a desired color gradation
in a said second period; applying a voltage for holding images
displayed in a said third period; repeating application said
voltages cyclically; in said first period; applying said common
voltage to said common electrode; selecting said scanning lines
sequentially; applying a voltage to the scanning line to turn on
all the switching elements connected to the said sequentially
selected scanning line; applying to obtain desired color gradations
said plurality of voltages to said data lines to create
electrostatic fields, and to initialize said pigment particles;
applying a voltage to the scanning line selected, to turn off all
the switching elements connected to the said sequentially selected
scanning line; in said second period; applying said common voltage
to said common electrode; selecting the scanning line sequentially;
applying a voltage to the said sequentially selected scanning line,
to turn on all the switching elements connected to the said
sequentially selected scanning line; applying a plurality of
voltage to the data lines; applying a plurality of voltages to the
scanning line selected, to turn off all the switching elements
which are connected to the said sequentially selected scanning
line; in said third period; applying said common voltage to said
common electrode; selecting said scanning line sequentially;
applying a voltage to said sequentially selected scanning line, to
turn on all of said switching element connected to the said
sequentially selected scanning line; applying said common voltage
to dais data lines; applying a voltage to the said sequentially
selected scanning line, to turn on all of said switching elements
connected to the said sequentially selected scanning line.
16. A method of claim 15, further comprising: after said second
period and before said third period; applying a said brake voltage
to said data lines, to stop rapidly movement of said pigment
particles;
17. A drive circuit for an electrophoretic display, the display
comprising: a plurality of data lines; a plurality of scanning
lines, each of which intersects said data lines; a common
electrode; a plurality of pixel electrodes, with one of said
plurality of pixel electrodes being provided at one of each of said
intersections of said data lines and said scanning lines, each of
said pixel electrodes being provided in opposing spaced relation to
said common electrode; a plurality of dispersal systems comprising
a colored fluid in which pigment particles are suspended, with each
of said dispersal systems being provided between said common
electrode and one of said pixel electrodes; and a plurality of
switching elements, with one of each of said switching elements
being provided at a corresponding one of each of said intersections
of said data lines and said scanning lines, with an on/off control
terminal being connected to one of said scanning lines passing
through one of said intersections; and with one of said data lines
passing through one of said intersections, being connected to one
of said pixel electrodes provided at each of one said
intersections; and the drive circuit comprising: an applying unit
which applies said common voltage to said common electrode; a
scanning drive unit, which selects said scanning line sequentially,
after applying a voltage to said scanning line selected, to turn on
all of said switching elements which are connected to said
sequentially selected scanning line during a certain period of
time; a data line drive unit, which applies said common voltage to
data lines, after applying a plurality of pixel voltages to said
data lines during a certain period of time, to migrate to a desired
position corresponding to a desired color gradation, during a
period in which one scanning line is selected and a voltage is
applied to said said selected sequentially selected scanning lines
to turn on all of said switching elements.
18. A drive circuit of claim 17, wherein said drive circuit
comprises: applying said reset voltage during a first period one
field; applying a voltage for obtaining desired color gradations
during a second period; repeating each of said voltage applications
alternately; in said first period; applying a voltage for obtaining
a desired color gradation to said data lines to create
electrostatic field via said data line drive unit, to initialize
said pigment particles; in said second period; applying a voltage
gradation voltages as pixel electrodes to said data lines, which
are correspondent to desired color gradations of a displayed
image.
19. A drive circuit of claim 17, said data line drive unit
comprising: applying said plurality of voltages for obtaining
desired color gradations to said plurality of data lines; applying
a plurality of brake voltages to said data lines, to create
electrostatic field, to halt rapidly movement of said pigment
particles.
20. A drive circuit of claim 19, the data line drive unit,
comprising: applying said brake voltages generated based on said
pixel voltages.
21. A drive circuit of claim 17, further comprising: applying said
reset voltage during a first period of a scanning field; applying a
plurality of voltages for obtaining desired color gradations in a
second period; repeating applying said plurality of voltage for
obtaining desired color gradations in the following period; in said
first period; the data line drive unit comprising: applying a
voltage to said data lines, to create electrostatic fields, to
initialize said pigment particles; in said second period; the data
line unit comprising: applying a voltage difference to said data
lines, between a voltage corresponding to a gradation which is
displayed in the previous applying voltage operation before and
color gradation to be displayed next.
22. A drive circuit of claim 21, the data line drive unit
comprising: applying said plurality of voltages for obtaining
desired color gradations to said data lines; applying said
plurality of brake voltages to said data lines.
23. A drive circuit for an electrophoretic display, the display
comprising: a plurality of data lines; a plurality of scanning
lines, each of which intersects said data lines; a plurality of
pixel electrodes, with one of said plurality of pixel electrodes
being provided at one of each of said intersections of said data
lines and said scanning lines, each of said pixel electrodes being
provided in opposing spaced relation to said common electrode; a
plurality of dispersal systems comprising a colored fluid in which
pigment particles are suspended, with each of said dispersal
systems being provided between said common electrode and one of
said pixel electrodes; and a plurality of switching elements, with
one of each of said switching elements being provided at a
corresponding one of each of said intersections of said data lines
and said scanning lines, with an on/off control terminal being
connected to one of said scanning lines passing through one of said
intersections; and with one of said data lines passing through one
of said intersections, being connected to one of said pixel
electrodes provided at each of one said intersections; and the
drive circuit comprising: an applying unit which applies said
common voltage to said common electrode; a scanning drive unit,
which selects said scanning line sequentially, after applying a
voltage to said sequentially selected scanning line, to turn on all
of said switching elements which are connected to the said
sequentially selected scanning line during a certain period of
time; a data line drive unit, which applies said common voltage to
data lines, after applying a plurality of pixel voltages to the
data lines during a certain period of time, to migrate to a
position corresponding to a desired color gradation, during a
period in which one of said scanning lines is selected and a
voltage is applied to the said sequentially selected scanning line
to turn on all of said switching elements; applying said reset
voltage during a first period of a scanning filed; applying said
plurality of voltages for obtaining desired color gradations during
a different, second period; applying said common voltage for
holding images displayed during a different, third period;
repeating applying said three voltages cyclically; in said first
period; applying a voltage to data lines, to create electrostatic
field, to initialize said pigment particles; in said second period;
applying a plurality of voltages for obtaining desired color
gradations to said data lines; in said third period; applying said
common voltage to said data lines.
24. A drive circuit of claim 23, the data line unit further
comprising: after applying said plurality of brake voltages and
before applying a voltage for holding images displayed; applying
said plurality of brake voltages to said data lines, to create
electrostatic fields, to halt rapidly movement of said pigment
particles.
25. A drive circuit for an electrophoretic display, the display
comprising: a plurality of data lines; a plurality of scanning
lines, each of which intersects said data lines; a plurality of
pixel electrodes, with one of said plurality of pixel electrodes
being provided at one of each of said intersections of said data
lines and said scanning lines, each of said pixel electrodes being
provided in opposing spaced relation to said common electrode; a
plurality of dispersal systems comprising a colored fluid in which
pigment particles are suspended, with each of said dispersal
systems being provided between said common electrode and one of
said pixel electrodes; and a plurality of switching elements, with
one of each of said switching elements being provided at a
corresponding one of each of said intersections of said data lines
and said scanning lines, with an on/off control terminal being
connected to one of said scanning lines passing through one of said
intersections; and with one of said data lines passing through one
of said intersections, being connected to one of said pixel
electrodes provided at each of one said intersections; and the
drive circuit comprising: an applying unit which applies said
common voltage to said common electrode; a scanning drive unit,
which selects one said scanning line sequentially, after applying a
voltage to the scanning line selected, to turn on all of said
switching elements which are connected to the said sequentially
selected scanning line during a set period of time; a data line
drive unit, which applies said common voltage to data lines, after
applying a plurality of pixel voltages to the data lines during a
certain period of time, to migrate to a desired position
corresponding to a desired color gradation, during a period in
which one scanning line is selected and a voltage is applied to the
said sequentially selected scanning lines to turn on all of said
switching elements; applying said reset voltage during a first
period of a scanning filed; applying said plurality of voltages for
obtaining desired color gradations during a different, second
period; applying said common voltage for holding images displayed
during a different, third period; repeating applying said plurality
of voltages for obtaining desired color gradations and said common
voltage alternately; in said first period; applying a voltage to
data lines, to create electrostatic field, to initialize said
pigment particles; in said second period; applying differential
voltage to the data lines, which is a difference between a voltage
correspondent to a color gradation displayed in a previous applying
voltage operation, and that to be displayed in said third period;
applying said common voltage to said data lines.
26. A drive circuit of claim 25, the data line drive unit further
comprising: after said second period and before third period;
applying a plurality of brake voltages, to data lines during one
scanning field, to create electrostatic field, to halt rapidly the
movement of said pigment particles.
27. A drive circuit of claim 25, wherein said reset voltage is
applied to the pixel electrodes regularly.
28. An electrophoretic display, comprising: an electrophoretic
panel, comprising: a plurality of data lines; a plurality of
scanning lines, each of which intersects said data lines; a common
electrode; a plurality of pixel electrodes, with one of said
plurality of pixel electrodes being provided at one of each of said
intersections of said data lines and said scanning lines, each of
said pixel electrodes being provided in opposing spaced relation to
said common electrode; a plurality of dispersal systems comprising
a colored fluid in which pigment particles are suspended, with each
of said dispersal systems being provided between said common
electrode and one of said pixel electrodes; and a plurality of
switching elements, with one of each of said switching elements
being provided at a corresponding one of each of said intersections
of said data lines and said scanning lines, with an on/off control
terminal being connected to one of said scanning lines passing
through one of said intersections; and with one of said data lines
passing through one of said intersections, being connected to one
of said pixel electrodes provided at each of one said
intersections; and an applying unit which applies the common
voltage to the common electrode; a scanning drive unit, which
selects the scanning line sequentially, after applying a voltage to
the scanning line selected, to turn on all of said switching
elements which are connected to the said sequentially selected
scanning line during a certain period of time; a data line drive
unit, which applies said common voltage to data lines, after
applying a plurality of pixel voltages to the data lines during a
certain period of time, to migrate to a position corresponding to a
desired color gradation, during a period in which one scanning line
is selected and a voltage is applied to the said sequentially
selected scanning lines to turn on all of said switching
elements;
29. An electrophoretic electronic device, comprising: an
electrophoretic display panel and a display unit; the panel
comprising: a plurality of data lines; a plurality of scanning
lines, each of which intersects said data lines; a common
electrode; a plurality of pixel electrodes, with one of said
plurality of pixel electrodes being provided at one of each of said
intersections of said data lines and said scanning lines, each of
said pixel electrodes being provided in opposing spaced relation to
said common electrode; a plurality of dispersal systems comprising
a colored fluid in which pigment particles are suspended, with each
of said dispersal systems being provided between said common
electrode and one of said pixel electrodes; and a plurality of
switching elements, with one of each of said switching elements
being provided at a corresponding one of each of said intersections
of said data lines and said scanning lines, with an on/off control
terminal being connected to one of said scanning lines passing
through one of said intersections; and with one of said data lines
passing through one of said intersections, being connected to one
of said pixel electrodes provided at each of one said
intersections; and the display unit comprising: an applying unit
which applies the common voltage to the common electrode; a
scanning drive unit, which selects the scanning line sequentially,
after applying a voltage to said sequentially selected scanning
line, to turn on all of said selected switching elements connected
to the said sequentially selected scanning line during a certain
period of time; and a data line drive unit, which applies said
common voltage to data lines, after applying a plurality of pixel
voltages to the data lines during a certain period of time, to
migrate to a desired position corresponding to a desired color
gradation, during a period in which one scanning line is selected
and a voltage is applied to the said selected scanning lines to
turn on all of said switching elements.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field of the Invention
[0002] The present invention relates to an electrophoretic display,
a method and apparatus for driving it, and an electronic device
using it.
[0003] 2. Description of Related Art
[0004] In the conventional art, electrophoretic displays are known
which consist of a pair of panels or substrates spaced apart in
opposing relation, each of which is provided with an electrode.
Between these electrodes a dyed dielectric fluid is provided.
Suspended in the fluid are electrically charged particles having a
pigment color different to the fluid in which they are suspended
(hereinafter referred to simply as pigment particles). In a display
update operation, differing voltages are applied via a switching
element to the electrodes to generate an electrostatic field in the
dielectric fluid, causing the pigment particles to migrate in the
direction of the applied field.
[0005] Electrophoretic displays utilizing an electrophoresis
phenomenon are classed as non-luminous devices. In electrophoresis,
pigment particles migrate under the action of Coulomb force which
is generated when an electrostatic field is applied to a dielectric
fluid in which the particles are dispersed.
[0006] However, prior art electrophoretic displays suffer from a
problem in that they afford poor viewing characteristics. The
present invention has been made to overcome this problem, and
provides for the first time an active matrix electrophoretic
display, which display has superior viewing characteristics.
SUMMARY OF THE INVENTION
[0007] As stated above, the object of the present invention is to
provide an active matrix electrophoretic display. Also provided is
a drive circuit integral to the device, and a method for driving
the display by using the circuit. In addition there is provided is
an electronic device attached to the electrophoretic display.
[0008] A method provided by the present invention is applied to an
electrophoretic display comprising a common electrode, a plurality
of pixels and a plurality of switching elements, each of which is
assigned to a corresponding one of a plurality of switching
elements. Each of the pixels is comprised of a pixel electrode
which is connected to a corresponding switching element, with the
pixel electrode being provided in spaced opposing relation to the
common electrode, and a dispersal system comprising a colored fluid
in which pigment particles are suspended being provided between the
common electrode and the pixel electrode.
[0009] In the method of the present invention, a 1st voltage is
applied to the common electrode. A 2nd voltage is then applied for
a set period of time via a corresponding switching element to a
pixel electrode, to generate an electrostatic field in the
dispersal system of the pixel, to cause the pigment particles to
migrate in the direction of the thus generated field to a desired
position, which corresponds to a desired color gradation of the
pixel. Next, the 1st voltage is applied via a corresponding
switching element to the pixel electrode, to cancel the
electrostatic filed and fix said pigment particles in a desired
position.
[0010] In the present invention, in addition to these steps, which
are common to the prior art, a new method is employed whereby
differential voltages are applied which are calculated on the basis
of a difference between a current average position of pigment
particles and a subsequent desired position. By continually
updating the voltage gradient using these parameters, positions of
pigment particles can be updated without the need for an
initialization step. Since no initialization step is required,
display updates can be affected rapidly.
[0011] In the present invention, to further improve display image
characteristics, it is preferable for there to be variations in the
properties of pigment particles employed, such as charge and mass.
As noted above, in the present invention pigment particles do not
need to be initialized before a display update is made. This helps
to overcome a problem which conventional electrophoretic displays
suffer from, whereby after a voltage differential between
electrodes is cancelled, pigment particles continue to move under
their inertia. This residual movement of pigment particles causes
fluctuations in an image displayed. In the case that minimal fluid
resistance acts against pigment particles, inertial movement of the
particles and resulting display fluctuations become pronounced. To
overcome this problem of inertial particle movement, in the method
of the present invention, after a differential voltage is applied
to a second electrode, a further `brake` voltage is applied to the
dielectric fluid to stop movement of the pigment particles rapidly.
Since a direction of motion of a particle is determined by a
direction and polarity of an applied electrostatic field, a brake
voltage to be applied has a polarity which is opposite to that of a
voltage applied to a pixel electrode. Different from prior art
displays, in the electrophoretic display of the present invention a
plurality of discrete dispersal systems are employed in electrical
communication with a common electrode. The dispersal systems
comprise a colored dielectric fluid in which contrasting pigment
particles are suspended; a plurality of data lines; a plurality of
scanning lines; and a plurality of switching elements, which are
provided at intersections between scanning and data lines. In
addition, a plurality of pixel electrodes is also provided, and
each of these pixel electrodes is connected to a corresponding
switching element, and is also subject to a charge applied by the
common electrode. In the method of driving the display of the
present invention, a voltage is applied to the common electrode,
and scanning lines are then subjected to sequential selection. In a
next step, a voltage corresponding to a required screen update is
applied by the pixel electrodes to the data lines, and a
differential voltage is applied to the pixel electrodes via their
respective switching elements, causing pigment particles suspended
in the dielectric fluid of respective display systems to migrate in
the direction of the applied field. To fix a position of the
particles, a uniform voltage is then applied to respective pixel
electrodes via their switching elements, and the switching elements
are then turned off.
[0012] It is to be noted that in the present invention, voltages
are applied as required, via switching elements, to respective
pixel electrodes, thereby creating a matrix in the electrophoretic
display In the method for driving the electrophoretic display of
the present invention, each of the pixel electrodes is first
subject to a preset uniform voltage applied by the common
electrode. Scanning lines are then selected sequentially. Next, a
voltage differential corresponding to a desired display update is
applied via the switching elements to their respective pixel
electrodes, whereby designated pigment particles are caused to
migrate. To maintain a desired display state, a uniform voltage is
applied to each of the pixel electrodes via respective switching
elements, and, further, a break voltage is applied to counter
inertial movement of the suspended pigment particles in each of the
particle dispersion systems, and finally the switching elements are
turned off.
[0013] According to the present invention, an active matrix
electrophoretic display can be realized by applying differential
voltages via a plurality of switching elements to a plurality of
corresponding pixel electrodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] In the accompanying drawings:
[0015] FIG. 1 is an exploded perspective view showing a mechanical
configuration of an electrophoretic display panel based on the
first embodiment of the present invention;
[0016] FIG. 2 is a partial sectional view of the panel;
[0017] FIG. 3 shows a block diagram of an electrical configuration
of an electrophoretic display having the panel;
[0018] FIG. 4 is a simplified partial sectional view of the divided
cell of the panel;
[0019] FIG. 5 exemplifies the relation of the voltage between the
two electrodes and the divided cell;
[0020] FIG. 6 is block diagram of the data line drive circuit 140A
of the electrophoretic display;
[0021] FIG. 7 is a timing chart of the scanning drive circuit 130A
and the data line drive circuit 140A;
[0022] FIG. 8 is a timing chart showing the outputted data from the
image processing circuit 300A;
[0023] FIG. 9 is a timing chart of the electrophoretic display in
the resetting operation;
[0024] FIG. 10 is a timing chart of the electrophoretic display in
the writing operation;
[0025] FIG. 11 is a timing chart of the resetting operation in the
second manner;
[0026] FIG. 12 is a timing chart of the resetting operation which
resets horizontal lines simultaneously;
[0027] FIG. 13 illustrates the horizontal lines to be
rewritten;
[0028] FIG. 14 illustrates the reset operation by the region;
[0029] FIG. 15 is a block diagram of the electrical configuration
of the electrophoretic display panel in the fifth manner;
[0030] FIG. 16 is a simplified partial sectional view of the
divided cell of the electrophoretic display;
[0031] FIG. 17 is a block diagram showing the configuration of the
image signal processing circuit 300A' based on the second
embodiment.
[0032] FIG. 18 is a timing chart of the outputted data from the
image signal processing circuit 300A';
[0033] FIG. 19 exemplify the relation of the gradation voltage and
the differential gradation voltage.
[0034] FIG. 20 is a timing chart of the electrophoretic display in
the writing operation;
[0035] FIG. 21 is a block diagram of the image signal processing
circuit 300B of the electrophoretic display based on the second
embodiment;
[0036] FIG. 22 is a timing chart of the outputted data from the
image signal processing circuit 300B;
[0037] FIG. 23 is a block diagram of the data line drive circuit
140B thereof.;
[0038] FIG. 24 is a bloc diagram of the detailed configuration of
the selection circuit 144B in the data line drive circuit 140B;
[0039] FIG. 25 is a timing chart showing the operation of the
selection circuit 144B;
[0040] FIG. 26 is a timing chart of the electrophoretic display in
the writing operation;
[0041] FIG. 27 is a block diagram of the image signal processing
circuit 300B' based on the forth embodiment;
[0042] FIG. 28 is a timing chart of the electrophoretic display in
the writing operation in the second embodiment;
[0043] FIG. 29 is a timing chart of the electrophoretic display
based on the fifth embodiment;
[0044] FIG. 30 is a timing chart of the electrophoretic display in
the writing operation;
[0045] FIG. 31 is a timing chart showing a whole operation of the
electrophoretic display based on the sixth embodiment;
[0046] FIG. 32 is a timing chart of the electrophoretic display in
the writing operation based on the sixth embodiment;
[0047] FIG. 33 is a timing chart of the whole operation pf the
electrophoretic display based on the seventh embodiment;
[0048] FIG. 34 is a timing chart of the electrophoretic display in
the writing operation;
[0049] FIG. 35 is a timing chart showing whole operation of the
electrophoretic display based on the eighth embodiment;
[0050] FIG. 36 is a timing chart of the electrophoretic display in
the writing operation based on the eighth embodiment;
[0051] FIG. 37 is a block diagram of a timer apparatus;
[0052] FIG. 38 is a block diagram of the timer apparatus in the
writing operation;
[0053] FIG. 39 is an external perspective view of an electronic
book as one example of electronic devices;
[0054] FIG. 40 is an external perspective view of a personal
computer as another example of electronic devices;
[0055] FIG. 41 is an external perspective of a mobile phone as
another example of electronic devices;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0056] Referring to the accompanying drawings, preferred
embodiments of the present invention will now be described.
[0057] (A) First Embodiment
[0058] An electrophoretic display of the present embodiment
displays an image according to an input image signal (VID). It is
able to display both static and animated images, but is
particularly suited to displaying static images.
[0059] (A-1) Outline of an Electrophoretic Display
[0060] FIG. 1 is an exploded perspective view showing the
mechanical configuration of an electrophoretic display panel A,
according to the first embodiment of the present invention.
[0061] FIG. 2 is a partial sectional view of the panel.
[0062] As shown in FIGS. 1 and 2, an electrophoretic display panel
A has an element substrate 100 and an opposing substrate 200.
Element substrate 100 is made of glass, a semiconductor or some
other suitable material. Opposing substrate 200 is made of glass or
some other suitable transparent material. A common electrode 201 is
formed on opposing substrate 200. A plurality of pixel electrodes
104 are formed on element substrate 100 to constitute a plurality
of pixels, each of which corresponds to one unit of an image.
Substrates 100 and 200 are provided in opposing relation to each
other such that electrodes formed on the surfaces of the substrates
face each other at regular intervals. Between these electrode
surfaces, bulkheads 110 are provided which divide the electrode
surfaces into a plurality of spaces, with each spaces facing,
respectively, pixel electrodes 104. These spaces are referred to
hereinafter as divided cells 11C. Each divided cell 11C is provided
with a dispersal system 1 comprising a dielectric fluid 2 in which
pigment particles are suspended. If required, the dielectric fluid
2 can be provided with an additive such as a surface-active agent.
In dispersal system 1, to avoid sedimentation of pigment particles
3 under gravity, both the dielectric fluid 2 and pigment particles
3 are selected to be approximately equal in specific gravity to
each other.
[0063] In this embodiment, an electrostatic field is applied to
dispersal system 1 in each divided cell 11 to move the pigment
particles in the system to a desired position which corresponds to
a desired color gradation of the pixel. It is possible to provide a
large number of divided cells 11C in the bulkhead 110, and the
range in which pigment particles 3 are able to migrate is thereby
limited to the inner space of each divided cell 11C. In the
dispersal system 1, migration of particles may be uneven or the
particles may condense to form a lump. However, using a plurality
of divided cells 11C in the bulkhead 110 prevents such a phenomenon
from occurring, and as a result the quality of images displayed is
improved. In electrophoretic display panel A, each pixel is capable
of displaying one of the three primary colors (RGB). This is
achieved by effecting three different types of dispersion in the
dispersal system corresponding to R, G and B colors, respectively.
Thus, when it is required to express dispersal system 1, dielectric
fluid 2, and pigment particles 3 as a separate primary color each,
subscripts "r," "g," and "b" are appended respectively to each
element.
[0064] Thus, in this embodiment, dispersal system Ir corresponding
to R color has red particles as the pigment particles 3r and the
dielectric fluid2r is a cyanogen color medium. The pigment
particles 3r are made of iron oxide, for example. The dispersal
system 1g corresponding to G color uses green particles as the
pigment particles 3g and the dielectric fluid2g is a magenta-color
medium. The pigment particles 3g are made of cobalt-green pigment
particles, for example. The dispersal system 1b corresponding to B
color uses blue particles as the pigment particles 3b and the
dielectric fluid2b is a yellow medium. The pigment particles 3b are
made of cobalt-blue pigment particles, for example.
[0065] That is, the pigment particles 3 that correspond to each
color to be displayed are used, while the dielectric fluid2 of a
certain color (the complementary color, in this embodiment) that
absorbs the color to be displayed is used.
[0066] The opposing substrate 200, the common electrode 201, and
the sealer 202 are transparent, enabling a user to see images
displayed the opposing substrate 200. Thus, if pigment particles 3
migrate towards to the display-surface-side electrode, they will
reflect light of a wavelength corresponding to the color to be
displayed. On the other hand, when the pigment particles 3 migrate
to the opposite-side electrode to the display surface, light of a
wavelength corresponding to the color to be displayed is absorbed
by the dielectric fluid2. In this case, such light will not be
visible to a user, and therefore no color will be visible. In the
present invention, a strength of an electrostatic field applied to
the dispersal system 1 determines how the pigment particles 3 are
distributed in the direction of thickness of the dispersal system
3. The combined use of the pigment particles 3, the dielectric
fluid2 which absorbs light reflected by pigment particles 3, and
controlling the dielectric field strength enables adjustment of
light reflectance of a color. As a result, a strength of light
reaching an observer can be controlled.
[0067] A display area A1 and a peripheral area A2 partitioned by
bulkheads 110 are provided on the surfaces of the element substrate
100 which faces the opposing substrate 200. In the display area, in
addition to the pixel electrodes 104, thin film transistors
(hereinafter, referred to as TFTs) are employed as scanning and
data lines, and switching elements are also employed and will be
described later. In the peripheral area A2 of the surface of the
element substrate 100, a scanning line drive circuit, a data line
drive circuit, and externally connected electrodes which will be
described later are formed.
[0068] FIG. 3 is a block diagram showing the electrical
configuration of the electrophoretic display. As shown, the
electrophoretic display is provided with the electrophoretic
display panel A; a peripheral circuit including an image processing
circuit 300A; and a timing generator 400. The image processing
circuit 300A generates image data D by compensating input image
signal VID based on the electrical characteristics of the
electrophoretic display panel A and outputs reset data Drest for a
predetermined period before it outputs the image data D.
[0069] The reset data Drest is used for attracting pigment
particles 3 to the pixel electrodes 104 so that their positions are
initialized. In this embodiment, dielectric fluid2 is dyed black
and pigment particles 3 consist of titanium oxide, which has a
whitish color, and for in this explanation will be described as
having a positive charge. Timing generator 400 generates several
timing signals synchronously with image D, described later for a
scanning drive circuit 130 and data line drive circuit 140A.
[0070] In display area A1 of electrophoretic display panel A, a
plurality of scanning lines 101 are formed in parallel to an
X-direction, while a plurality of data lines 102 are formed in
parallel to a Y-direction which is orthogonal to the X-direction. A
TFT 103 and a pixel electrode 104 are positioned to provide a pixel
in the vicinity of each of the intersections made by these scanning
lines 101 and data lines 102. Hence the pixels are mapped in a
matrix by the intersections made between scanning lines 101 and
data lines 102. The gate electrode of TFT 103 of each pixel is
connected to a particular scanning line 101 for the pixel and a
source electrode thereof is connected to a particular data line 102
for the pixel. Moreover, a drain electrode of the TFT is connected
to pixel electrode 104 of the pixel. Each pixel is composed of a
pixel electrode 104, a common electrode 201 formed on opposing
substrate 102, and dispersal system 1 provided between the
substrates on which the common and pixel electrodes are provided,
respectively.
[0071] Scanning line drive circuit 130 and data line drive circuit
140, consisting of TFTs, are made using the same production process
as pixel TFTs 103. This is advantageous in terms of integration of
elements and production costs.
[0072] When a scanning signal Yj is brought to its active state,
TFTs 103 on the jth scanning line 101, to which signal Yj is
supplied, data line signals X1, X2, . . . , Xn are provided
sequentially to pixel electrodes 104. On the other hand, the common
voltage Vcom is applied from a power supply, not shown, to the
common electrode on opposing substrate 200. This generates a
dielectric field between each pixel electrode 104 and common
electrode 201 on opposing substrate 200. As a result, the pigment
particles 3 within dispersal system 1 migrate to and an image is
displayed using gradations based on image data D on a
pixel-by-pixel basis.
[0073] (A-2) Principle of Displaying
[0074] FIG. 4 is a cross-sectional view of a simplified structure
of divided cell 11C. In this embodiment, firstly the reset
operation is carried out.
[0075] Supposing that pigment particles 3 are positively charged,
an operation is conducted to apply a voltage to pixel electrode
104, which has negative polarity relative to that of common
electrode 201, and pigment particles 3 are attracted to pixel
electrode 104 as shown in FIG. 4A. Next, a positive-polarity
voltage is applied to pixel electrode 104, the voltage
corresponding to a gradation to be displayed as shown in FIG. 4B.
And the pigment particles migrate towards common electrode
201following the dielectric field. When the potential difference is
made zero, no dielectric field is applied to the particles, and
they stop moving as a result of fluid resistance. In this case,
since the velocity of the particle is determined by a strength of
an applied dielectric field, that is, the migration time of a
particle is determined by an applied voltage, if the duration is
constant, changing the applied voltage will lead to a change in
average position of pigment particles 3 in the direction of
thickness.
[0076] Incident light from common electrode 201 is reflected by
pigment particles 3 and this reflected light reaches observer's eye
through common electrode 201. Incident and reflected light are
absorbed in dielectric fluid2 and the absorption rate is
proportional to the optical path length. Hence a gradation
recognized by an observer is determined by the positions of pigment
particles 3. As mentioned above, since the positions of pigment
particles 3 are determined by an applied voltage over a constant
period, a desired gradation will be displayed.
[0077] Dispersal system 1 comprises a large number of pigment
particles. If they all have the same properties, such as electrical
property (for instance, charge), mechanical properties (for
instance size, mass,) and other properties, they will behave in the
same manner.
[0078] However the thickness of a divided cell 11C is made to be
from a few up to a maximum of 10 micrometers, and thus a maximum
migration length of pigment particle 3 is very short. Consequently,
to improve image display characteristics, an infinitesimal
migration length must be controlled. To achieve this, low voltages
to effect a gradation must be used, which makes gradation control
difficult.
[0079] To assist in control, pigment particles are provided with
differing properties. These differences enable a statistical
distribution to be achieved of positions of pigment particles. FIG.
5 shows an example of a relation between a voltage applied between
a common and pixel electrodes and the gradation displayed. The time
fame for voltage application is 50milliseconds and the average
voltage applied to migrate pigment particles 3 to common electrode
201 is 5 volts; and the standard deviation of the distribution is
0.2 volts normalized with 5 volts.
[0080] In this figure, a solid line shows the characteristics of
gradation according to the applied voltage and dotted line shows
the probability density function. Probability density is the number
of particles that have reached the common electrode 201 which is
normalized with 5 volts.
[0081] As shown therein, when the applied voltage is lower than 4.5
volts pigment particles merely reach the common electrode 201, but
when the applied voltage is 5 volts, half the particles 3 reaches
to it, and the voltage is higher than 5.5 volts almost all of them
reaches. Therefore an applied voltage should be controlled in the
range from 4.5 to 5.5 volts to obtain the desired color gradation
image.
[0082] (A-3) Drive Circuit
[0083] As shown in FIG. 3, the scanning drive circuit 130 has a
shift resister and sequentially shifts a Y-transfer start pulse DY
which becomes become active at the beginning of vertical scanning
lines based upon a Y-clock signal YCK and its inverted Y-clock YCKB
and generates scanning line signals Y1, Y2, . . . , Ym. As shown in
FIG. 7, scanning signals which sequentially shift their activating
period (the the H-level period) are generated and outputted to each
scanning line 101.
[0084] FIG. 6 shows a block diagram of the scanning line drive
circuit 140A. Data line driving circuit 140A has an X-shift
resister 141, a bus BUS which is supplied image data composed of 6
bits, switches SW1, . . . , SWn, a first latch 142, a second latch
143, a selection circuit 144 and a D/A converter 145.
[0085] Firstly, the X-shift resister 141 sequentially shifts a
X-transfer start pulse DX to generate sampling pulse SR1, SR2, . .
. , SRn sequentially according to the X-clock XCK and its inverted
X-clock XCKB.
[0086] Secondly, the bus BUS is connected to the first latch 142
through the switch SW1, . . . , SWn and sampling pulses SR1,SR2, .
. . , SRn are supplied to each input terminal with the
corresponding switch. A switch SWj is a set of 6 switches according
to the 6 bits image data. Hence the image data D is, at a time,
imported to the first latch 142 synchronously with with each
sampling pulse SR1, SR2, . . . , SRn.
[0087] The first latch 142 latches image data D supplied from
switch SW1, . . . , SWn and outputs it as dot-sequential data Da1,
. . . , Dan. The second latch 143 latches each dot-sequential data
Da1, . . . , Dan with a latch pulse LAT, which becomes active in
every horizontal scanning time. The second latch 143 generates
line-sequential data Db1, . . ., Dbn from dot-sequential data Da1,
. . . , Dan.
[0088] The common voltage data Dcom generated in the image
processing circuit 300A and a no-bias timing signal Cb generated in
the timing generator 400 is supplied to the selection circuit
144.
[0089] The data Dcom is data which sets the voltage which is
supplied to the common electrode 201 (ground level, for instance).
The no-bias timing signal Cb becomes active (the H-level) from a
certain point to the end in a horizontal scanning time.
[0090] The selection circuit 144, when non-bias timing signal is
active, selects the common voltage data Dcom, while when it is
inactive, selects line-sequential data Db1, . . . , Dbn to output
data Dc1, . . . , Dcn as shown in FIG. 7. The D/A converter 145
converts data Dc1, . . . , Dcn, 6 bits digital data into analog
signal and generates this as each data line signal X1, . . . , Xn
and supplies it to each data line 102.
[0091] (A-4) Operation in an Electrophoretic Display
[0092] FIG. 8 shows a timing chart of an output data from the image
signal processing circuit 300A. Outline of the operation will be
described referring to FIG. 8.
[0093] Firstly, at time t0, the image signal processing circuit
300A, timing generator 400 and electrophoretic display panel A is
turned the power on when the power supply of the electrophoretic
device is switched on.
[0094] After the circuit is stabilized, the image signal processing
circuit 300A outputs the reset data Drest over a period of one
scanning field. In the example shown in FIG. 8, the scanning field
starts at time t1. At reset time Tr, pigment praticles 3 are
attracted to the pixel electrodes 104 and their positions are
initialized as described above.
[0095] While a data line drive circuit 104A outputs the reset
voltages Vrest to each data line 102 according to data values of
Drest, the scanning line drive circuit 130 sequentially selects
each the line 101, with the result that the reset voltage Vrest is
applied to all the pixel electrodes 104.
[0096] Next, a writing period Tw begins at a time t2. In this
writing period Tw, the image signal processing circuit 300A outputs
image data D over one scanning field.
[0097] The gradation voltages V are applied to each pixel electrode
104 corresponding to the gradation to be displayed so that a
section of display image is completed.
[0098] After next, in a holding period Th which starts with time t3
and ends with time t4, the image is held which is written in the
immediately preceding writing period Tw. Its length can be set
freely. In this period, the image signal processing circuit 300A
halts and outputs no data and no electrostatic field is generated
between the pixel electrodes 104 and the common electrode 201. The
pigment particles 3 do not change position unless they are subject
to an electrostatic field, and consequently, a static image is
displayed over the period.
[0099] Next, in the period which begins with time t4 and ends with
t6, the image is rewritten. In a similar way in the period that is
from time t1 to time t3, the writing operation subsequent to the
reset operation is carried out so that the displayed image is
renewed.
[0100] (1) Resetting Operation
[0101] FIG. 9 is a timing chart of an electrophoretic display in a
resetting operation. As mentioned above, in the reset period Tr,
the reset data Drest is supplied to the data line drive circuit
140A. In this period, no-bias signal is inactive (the L-level) as
shown in FIG. 9, as a result, the voltages of data lines signals
X1, . . . , Xn are all equal to the reset voltage Vrest.
[0102] In this embodiment, the reset voltage Vrest is negative
compared to the common voltage Vcom of the common electrode,
because the pigment particles are positively charged.
[0103] At this time, when the scanning signal Y1 becomes active
(the H-level), TFTs 103 in the first line are switched on and the
reset voltage Vrest is applied to each pixel electrode 104. After
that, reset voltage Vrest is applied to each pixel electrode 104 of
the second, third, . . . , mth lines. For exemple, at time tx, when
the scanning line signal Y1 is made inactive, each TFT 103 in the
first line is switched off so that the pixel electrodes 104 and
data lines 102 are cut off. However capacity has been created in
the system comprised of the pixel electrode 104, dispersal system 1
and the common electrode 201. Hence if each TFT 103 is switched
off, the reset voltage Vrest is maintained between the pixel
electrode 104 in the first horizontal line and the common electrode
201.
[0104] In that way reset voltage Vrest is applied between the two
electrodes, pigment particles 3 in the dispersal system 1 are
attracted and their positions are initialized.
[0105] (2) Writing Operation
[0106] FIG. 10 shows a timing chart of the electrophoretic display
in an operation of writing. Here is depicted about ith line (ith
scanning line) and jth column (jth data line) but it is obvious
that other pixels can betreated likewise. In the following, the
pixel of ith line and jth column is represented by Pij, the
gradation voltage to be displayed in the pixel Pij is represented
by Vij and the brightness if Pij is represented by Iij.
[0107] Since each data line X1, . . . , Xn is generated through the
D/A conversion of data Dc1, . . . , Dcn as shown in FIG. 7, the
voltage of the data line signal Xj is, as shown in FIG. 10, equals
to the gradation voltage Vij in the voltage applied period Tv from
time T1 to time T2, while to the common voltage Vcom in the no-bias
period Tb from time t2 to time t3.
[0108] The scanning line signal Yi supplied to the ith scanning
line 101 is active during the period of the ith the horizontal
scanning. Therefore, the TFT 103 which comprises the pixel Pij is
switched on over that period and the data line signal Xj from time
TI to time tme T3 is applied to the pixel electrode 104. That is,
in this embodiment, an operation that begins with applying the
gradation voltage Vij to the pixel electrodes 104 and ends with
applying the common voltage Vcom thereto is completed within a
period of one horizontal line scanning.
[0109] In the following, the pigment particles' motion will be
described in the pixel Pij. Being done the reset operation before
the writing operation begins, at time T1, all pigment particles of
the pixel Pij are positioned on the side of the pixel electrode
104. At this time when the voltage 104 Vij is applied to the pixel
electrode 104, an electrostatic field is generated in the direction
of from the pixel electrode 104 to the common electrode 201. Thus
the particles 3 start to move at time T1.
[0110] In this embodiment, since the particles 3 are white and
dielectric fluid2 is black, the more pigment particle 3 is nearing
to the common electrode 201, the higher the brightness Iij of the
pixel Pij is. As a result, Iij is becomes higher gradually from
time TI as shown therein.
[0111] Since the pixel Pij is composed of a dispersal system 1
sandwiched by a pixel electrode 104 and the common electrode 201,
it has the capacitance depending upon the area of the electrodes,
the distance between the two electrodes, and dielectric constant of
the dispersal system 1.
[0112] Accordingly, even if TFT 103 is turned OFF to brake
supplying charges to the pixel electrode 104, since the capacitor
accumulates some charge, electrostatic field with a constant
strength being generated between the two electrodes. Thus, since
pigment particles 3 continue to migrate to common electrode 201 for
as long as an electrostatic field is applied, a period in which
generation of the electrostatic field is stopped, in other words, a
process to remove extra charges accumulated in the capacitance is
required. Consequently, the no-bias period Tb is set.
[0113] In the no-bias period Tb, since the common voltage Vcom is
applied to the pixel electrode 104, the pixel electrode 104 and the
common electrode 201 becomes equipotential at time T2. This means
no electrostatic field is applied to pigment particles 3 from that
time. If the fluid resistance of the dielectric fluid is, to some
extent, large, the particles 3 stop moving at time T2 when no
electrostatic field exists. This results in a constant value of
brightness Iij from time T2 as shown therein.
[0114] If the value of the fluid resistance of the dielectric
fluid2 is small, the pigment particles 3 keep moving for a period
due to their inertia. In this case, the image D which is
compensated beforehand by taking the above effect into account is
generated in the image signal processing circuit 300A.
[0115] In this operation of writing, brightness Iij of the pixel
Pij can be controlled based on the gradation to be expected such
that after the voltage Vij is applied to the pixel electrode 104 to
move the pigment particles 3 by the distance according to the
gradation to be displayed, then the common voltage Vcom is applied
thereto to brake the moving pigment particles.
[0116] In this embodiment the common voltage Vcom is applied to
brake pigment particles 3, but it is not necessary to apply the
same voltage, which completely equals to the common voltage Vcom,
instead any voltage, which is able to brake moving pigment
particles 3 is possible.
[0117] Since the particles 3 are not able to migrate simply by
overcoming fluid resistance, if the value of the fluid resistance
of the dielectric fluid is large it may be necessary to apply a
voltage which is somewhat different from the common voltage
Vcom.
[0118] (3)Holding Operation
[0119] In FIG. 7, at time T3, since the scanning line signal Yi
shifts from active to inactive, the TFT 103 of the pixel Pij is
turned off. As mentioned above, in the no-bias period Tb, since the
common voltage Vcom is applied to the pixel electrode 104, no
electrostatic field is generated between the two electrodes.
Therefore no electrostatic field is applied to the dispersal system
1 unless a new voltage is applied. This enables the position
pigment particles 3 to be held, and thus a displayed image to be
held.
[0120] In such a holding period Th, since there is no need to apply
a voltage to pixel electrodes 104, and consequently neither the
scanning line signal Y1, . . . , Ym nor the data line signal Xi, .
. . , Xn need be generated, thereby enabling a reduction in power
consumption in this period as follows:
[0121] First the main power supply of the electrophoretic display
is turned off. This means that the electrophoretic display panel
and peripheral devices such as the image signal processing circuit
300A and the timing generator 400 halt and no power is
consumed.
[0122] The second is to brake supplying power to the
electrophoretic display panel A. This reduces power
consumption.
[0123] The third is to stop supplying the Y-clock YCK, the inverted
Y-clock YCKB, the X-clock XCK, the inverted X-clock XCKB to the
scanning line drive circuit 130, and the data lines driving circuit
140A. Since the scanning line drive circuit 130and the data line
drive circuit 140A is made of complementary TFTs as described
above, power is consumed only when the current is fed therethrough,
in other words, inversion of a logic level occurs. Consequently,
stopping the supply tothe clocks enables a reduction in power
consumption.
[0124] (4) Rewriting
[0125] Rewriting is carried out as follows:
[0126] The first method is as follows. After a reset operation is
carried out, as described above, sequentially on a line-by-line
basis, the writing operation is also carried out sequentially on a
line-by-line basis, and a common voltage followed by a gradation
voltage is applied to the pixel electrodes 104. This enables frame
rewrite of an image.
[0127] The second method consists of a resetting and rewriting
operation carried out only in the lines where rewriting is
required. Suppose the jth and the j+1th lines are to be rewritten
by way of example. FIG. 11 shows a timing chart describing an
operation of resetting in this method.
[0128] The second method is that, in the resetting period Tr, the
image signal processing circuit 300A outputs the reset data Drest.
And at this time, the scanning line driving circuit 130
sequentially outputs the scanning signal Y1, . . . , Yj,Yj+1, . . .
,Ym as shown therein. While the no-bias timing signal Cb is in the
L-level during the scanning line 101 necessary to be rewritten is
selected. Since jth and j+1th lines are rewritten, the no-bias
timing signal Cb is in the L-level (inactive) when the scanning
line signal Yj and Yj+1 are active.
[0129] As described above, while the selection circuit 144 (cf.
FIG. 6) outputs the common voltage data Dcom during the no-bias
timing signal Cb is in the H-level (active) and outputs the
outputted data Db1, . . . ,Dbn of the latch 143 during the no-bias
timing signal Cb is in the low level. In other words, in the period
which jth and j-1th scanning line 101 are selected, the reset
voltage Vrest is supplied to all data lines 102, while in the other
selected time of the scanning line 101, the common voltage Vcom is
applied to all data lines 102.
[0130] Therefore while the common voltage Vcom is applied to the
pixel electrodes 104 on from the first to the j-1 th line and from
the j+2 th to the mth line, the reset voltage Vrest is applied to
the pixel electrodes 104 of the jth and j-1th line, so that the
pixels of the j th and j+1th lines are initialized. Since applying
the common voltage Vcom to the pixel electrodes 104 generates no
electrostatic field, the positions of pigment particles 3 in the
pixels on from the first to the j-1 th line and from the j+2to the
mth line don't change.
[0131] In the writing operation, writing is carried out in the
manner as shown in FIG. 7, so that the image signal processing
circuit 300A outputs the image data D to the line to be rewritten,
while the common voltage data Dcom to the other lines. This enables
rewriting only in the jth and j-1th lines.
[0132] The third method is that after a plurality of electrodes is
reset, they are rewritten in the usual way. In the above second
method, a reset operation is carried out line by line in such a way
that first the jth line is reset then the j-1th line is reset and
so on.
[0133] However, it is possible to reset simultaneously if a
scanning line drive circuit which simultaneously select a plurality
of scanning lines 101 to be rewritten. For example, as shown in
FIG. 12, it is obvious that it is possible to reset simultaneously
jth and j-1th line to be rewritten if the reset voltage Vrest is
applied to the data lines 102 activating only the scanning line
signal Yj and Yj-1. Writing is carried out in the usual way, as
shown in FIG. 7 that the image signal processing circuit 300A
outputs the image data D only in the line to be rewritten, then the
common voltage data Dcom is outputted to the other lines. This
method enables rewriting only in the jth and j+1 line.
[0134] The fourth method is that after a region to be rewritten is
simultaneously reset, a new voltage is applied to the pixels which
belong to the region.
[0135] Suppose that the region R to be rewritten is from ath to bth
line and from cth to dth column as shown FIG. 14.
[0136] First, the scanning line drive circuit is used which can
rewrite simultaneously a plurality of the scanning lines 101 to be
rewritten. The image signal processing circuit 300A outputs the
data as the data of one line, which is the common voltage data Dcom
for from the first to the c-1th line and while is the reset data
for from the cth to the Dth line and the common voltage data Dcom
for from d+1 th to the nth line. The no-bias timing signal remains
to be inactive. This enables that the data lines signal from X1 to
Xc-1 and from Xd+1 to Xn is set to the common voltage Vcom during
the horizontal scanning, while the data lines signal from Xc to Xd
is set to be the reset voltage Vrest. In the horizontal scanning
period, the scanning line signal only from Ya to Yb can be set to
active so as to reset the region R. In writing, the image signal
processing circuit 300A outputs the image data D to the pixels
corresponding to the region R, while the common voltage data Vcom
to the others. Rewriting only of the region R is carried out in
this way.
[0137] The fifth method is carried out such that after all the
pixels are reset simultaneously, rewriting is carried out in the
ordinary manner of writing. FIG. 15 shows a block diagram of the
electrophoretic display panel B in this manner. The electrophoretic
display panel B has the same configuration as the electrophoretic
display panel A shown in FIG. 3 except that TFTs 105 are set in
each line and that the image scanning driving circuit 130B is able
to simultaneously become active the scanning line signals from Y1
to Ym.
[0138] In FIG. 5 the reset voltage Vrest is applied to source
electrodes on each TFT 105 and reset timing signal Cr is applied to
gate electrodes thereon and those drain electrodes is connected
with each data lines102. The reset timing signal Cr generated in
the timing generator 400 becomes active during the reset period Tr.
When the reset timing signal Cr is active, all TFTs is turned on
simultaneously so that the reset voltage Vrest is applied to each
data line 102. On the other hand, the scanning driving circuit 130B
makes all scanning line signals active when the reset timing signal
Cr is turned to active.
[0139] Hence the reset voltage Vrest is applied to all the pixels
104 during the reset timing signal Cr is active. This leads to the
simultaneous resetting of all the pixels.
[0140] In this case, it may be possible that source electrodes on
each TFT to be set at ground level, and the voltage, instead of the
common voltage Vcom, is used to apply a positive voltage with
reference to the ground potential which is sufficient to
initialize. That is, with reference to either a pixel electrode 104
or the common electrode 201, sufficient voltage to initialize
another electrode is applied.
[0141] It is also possible for the voltage for initializing to be
applied to the pixel to which the region of the image to be
rewritten belongs.
[0142] (B) Second Embodiment
[0143] In the above embodiment, rewriting is carried out in a way
that after a reset operation as shown in FIG. 16A is carried out,
then a writing operation is carried out shown in FIG. 16B to renew
a displayed image. In this case, the positions of the pigment
particles 3 are initialized in displaying a subsequent image. In
the case that dielectric fluid2 is colored black and the pigment
particles 3 are colored white, a black out occurs across the entire
image. However, if a change in image is effected sufficiently
rapidly, it will not be visible to the naked eye. Nevertheless
there is a case that the resetting operation needs a long time
according to physical property of the dispersal system 1, which
results in the fact that change of the brightness in initializing
the pigment particles 3 can be detected.
[0144] In order to deal with the above situation, it is possible
that the voltage which corresponds to the difference between the
average position to be displayed next and that corresponding to the
presently displayed image is applied between the two electrodes for
a constant time. Suppose the present gradation is 50% and the
gradation to be displayed next is 75%, for example. If the average
position of the pigment particles 3 is 50% the thickness direction
of the dispersal system 1, the gradation displayed is 50%, as shown
in FIG. 16B. In order to change this gradation to that of 75%, it
is necessary to move the particles 3 to a position of {fraction
(3/4)} in the thickness direction. Consequently the voltage, which
corresponds to the difference between the gradation to be next
displayed and that of now displayed, is applied to the pixel
electrodes 104 to move the pigment particles 3 to the appropriate
position. This realizes a renewing of a displayed image without a
resetting operation, which will lead to smooth displaying of an
animation. In the following, only a difference compared to the
first embodiment will be described.
[0145] (B-1) Image Signal Processing Circuit 301A
[0146] FIG. 17 is a block diagram showing a configuration of a
image signal processing circuit 301A. The image signal processing
circuit 301A is comprised of an A/D converter 310, a compensation
part 320, a calculation part 340. An externally supplied signal VID
is supplied to the compensation part 320 through the A/D converter
310 as an input image data Din. The compensation part has a ROM and
others and generates an image data Dv undergoing compensation
processing such as gamma correction, and output it to a calculation
part 330.
[0147] The calculation part 330 has a memory 331 and a subtracter
332. The memory 331 has the first field memory 331A in which
writing is executed in odd fields, while reading is executed in
even field and has the second field memory 331B in which writing is
executed in an even field. The memory 331 delays the image data Dv
by one field which is supplied to the other input terminal of the
subtracter 332 as the delayed image data Dv'.
[0148] Then the subtracter 332 generates the differential image
data Dd by subtracting the delayed image data Dv' from the image
data Dv and output it. The selection part 340 selects the reset
data Drest in the reset period Tr, while outputs the differential
image data Dd in the wirting period Tw. It should be noted that, in
the first field, since there is no delayed image data Dd, a dummy
data whose value is `0` is supplied to the other input terminal of
the subtracter 332. Hence the image data Dv is outputted as the
differential image data Dd in the first field. If the delayed image
data Dv' is the present gradation displayed, the image data Dv is
equivalent to the gradation to be displayed next. Therefore the
differential image data Dd is equivalent to the data which
corresponds to the difference between the gradation to be next
displayed and that of now displayed.
[0149] Since configurations of drive circuit and data line circuit
in this embodiment is similar to that of the first embodiment,
explanation is omitted.
[0150] (B-2) Operation in the Second Embodiment
[0151] FIG. 18 is a timing chart showing the output data from the
image signal processing circuit 301A.
[0152] First, at time t2, the writing period Tw begins. In this
period, the image signal processing circuit 301A output the
differential image data Dd. Hence the differential voltage Vd,
which corresponds to the difference between the gradation to be
next displayed and the present gradation, is applied to each pixel
electrode 104 except that in the first field (from time t2 to t3),
the image data Dv is supplied as the differential image data Dd to
the data lines drive circuit 130, which means that the voltage to
be displayed is applied to each electrode 104. However, since, at
time t2, the gradation displayed is set to 0% (or 100%) having done
the resetting, the operation in the first period is essentially
equivalent, in the viewpoint of it's basic function, to that the
differential voltage Vd which corresponds to the difference between
the gradation to be next displayed and the present gradation is
applied even in the first field.
[0153] Similarly, after the image is displayed in the first field,
the voltage which corresponds to the gradation difference is
applied in the next field and so in the following field.
[0154] For instance, if the gradation voltage at a pixel changes
such as v1,v2, . . . , v7 accordingly from the first field F1 to
the seventh field F7 as shown in FIG. 19A, the differential voltage
Vd are Vd1,Vd2, . . . ,Vd7 accordingly as shown in FIG. 19B.
[0155] In the holding period Th (after time t5), a static image is
displayed likewise in the first embodiment.
[0156] (B-3) Writing Operation
[0157] FIG. 20 shows a timing chart of the electrophoretic display
in the writing operation. Here is depicted about ith line (ith
scanning line) and jth column (jth data line) but it is obvious
that other pixels can be, of course, dealt likewise. In the
following, the pixel of ith line and jth column is represented by
Pij, the differential voltage to be displayed in the pixel Pij is
represented by Vdij and the brightness of Pij is represented by
Iij. Suppose the pixel Pij displayed 10% in the next previous field
and also required voltage to change from the displayed gradation 0%
(all pigment particles 3 are on the side of the pixel electrodes
104) to the displayed gradation 100% (all pigment particles are on
the side of the common electrodes is represented by +V100 with
respect to the common voltage Vcom. Similarly, required voltage to
change from 100% to 0% is represented by -V100.
[0158] Since each data line X1, . . . , Xn is generated through the
D/A conversion of data Dc1, . . . , Dcn as shown in FIG. 7, the
voltage of the data line signal Xj is, as shown in FIG. 20, equals
to the differential voltage Vdij in the differential
voltage-applied period Tdv from time T1 to time T2, while to the
common voltage Vcom in the no-bias period Tb from time t2 to time
t3.
[0159] Provided that the gradation to be displayed in the present
field 50%, the value of the differential voltage Vdij is -V50
indicated as the solid line therein because the voltage decreases
by 50% from the next previous one. By another way of example, if
the gradation to be displayed in the present field is 0%, the value
of the Vdij is -V100 indicated as the dotted line therein.
[0160] (C) Third Embodiment
[0161] In the first embodiment, as described before, after the
gradation voltage is applied to the pixel electrodes 104 to move
the pigment particles 3 by the distance correspondent to the
gradation to be displayed, the common voltage Vcom is applied to
the pixel electrodes 104 not to apply any electrostatic field to
the particles 3. Additionally, the image data D is compensated at
the image signal processing circuit 300A before outputting taking
the inertia into consideration, in case of small fluid resistance
of the dielectric fluid, which means that the particles 3 continue
to move under inertia.
[0162] However, it can take a considerable time for pigment
particles 3 to become stationary depending on the level of fluid
resistance encountered in dielectric fluid 2. In the above example,
since pigment particles 3 migrate away from pixel electrodes 104 to
the common electrode, if there is little fluid resistance the image
displayed will not reach optimum brightness in a desired time. In
the third embodiment, an electrophoretic display designed to
prevent fluctuations in brightness is provided. It is configured in
the same manner as that of the first embodiment shown in FIG. 3,
except that image signal processing circuit 300B and data line
drive circuit 140B is used instead of the image signal processing
circuit 300A and the data line processing circuit 140A.
[0163] (C-1) Image Signal Processing Circuit
[0164] FIG. 21 is a block diagram of image signal processing
circuit 300B and FIG. 22 is a timing chart for output data.
[0165] As shown in FIG. 21, an image signal processing circuit 300B
is provided with an A/D converter 310, a compensation part 320, a
brake voltage generation part 330 and a selection part 340. The
image signal VID supplied externally through the A/D converter is
supplied to the compensation part 320 as input image data Din. The
compensation part is provided with a ROM or other suitable memory
and generates an image data Dv undergoing compensation processing
such as gamma correction.
[0166] The brake voltage generation part 330 is provided with a
table in which the brake voltage data Ds and image data D having
values corresponding to those of of Ds are memorized. In this way,
the brake voltage data Ds is acquired by accessing the table and
using image data D as an address. The table is provided with
storage circuits such as RAM or ROM.
[0167] The brake voltage data Ds corresponds to the brake voltage
Vs, which will be described later, and is used to brake pigment
particles 3. As mentioned above, pigment particles 3 subject to
inertial movement can be braked by utilizing a electrostatic field
Coulomb force the direction of which is opposite to that of pigment
particles 3. Since pigment particles 3 move in response to a
gradation voltage for display of an image, it is necessary to apply
an electrostatic field to them which is acting in an opposite
direction, and the value of which is dependent on the kinetic
energy of pigment particles 3, in other words, the gradation
voltage V Therefore, in this embodiment, taking into account fluid
resistance of dielectric fluid2 among other factors, the brake
voltage data Ds corresponding to the values of the image data D is
memorized in the table beforehand for reading.
[0168] As shown in FIG. 22, a selection part 340 outputs reset data
in reset period Tr, while in the writing period, it outputs
multiplex data Dm in which image data D and brake voltage data Ds
are combined. If image data D consists of 6 bits and brake voltage
data Ds is also 6 bits, the multiplex data Dm will be 12 bits,
which means that 6 bits from the most significant bit (MSB) is the
image data D and 6bits from the latest significant bit (LSB) is the
brake voltage data Ds.
[0169] (C-2) Data Line Drive Circuit
[0170] FIG. 23 shows a block diagram of a data line drive circuit
140B. In this embodiment, it is configured similarly to a data line
drive circuit 140A in the first embodiment except that a first
latch 142B and a second latch 143B latch 12 bits data and that a
selection circuit 144B is used instead of a selection circuit
140B.
[0171] The first latch 142B generates dot-sequential data from Da1
to Dan latching 12 bits multiplex data Dm and the second latch 143B
transforms the dot-sequential data from Da1 to Dan into
line-sequential data from Db1 to Dbn. It should be noted that the
reset data Drest in the resetting period is transformed into
remains 6bits line-sequential data remaining 6bits.
[0172] FIG. 24 shows a block diagram showing a detailed
configuration of the selection circuit 144B and FIG. 25 shows the
timing chart thereof. As shown in FIG. 24, the selection circuit
144B has n selection units from U1 to Un, each of which selects
appropriate data from the image data D and the brake voltage data
Ds, which is comprising the multiplex data Dm and the voltage data
Ds, and outputs it, depending on the no-bias timing signal Cb and
the stop timing signal Cb. The no-bias timing signal Cb becomes
active (the H-level) only in the period in which the common voltage
data Dcom is selected like in the fist embodiment described above,
while the stop timing signal Cs becomes active (in the H-level)
only in the period in which the brake voltage data Ds is
selected.
[0173] The selection circuit 144B selects and outputs the image
data D when the both Cs and Cb is inactive (the L-level). When the
Cs is active, it selects and outputs the brake voltage data Ds.
When both Cs and Cb become active, it selects and output the common
voltage data Dcom.
[0174] Suppose the multiplex data Dmi is supplied as the ith
line-sequential data Dbi to the ith selection unit Ui in a certain
horizontal scanning period as shown in FIG. 25, for example. In
this case, it is the image data Di which is comprised of upper bits
of the multiplex data Dm and the brake voltage data Dsi which is
comprised of the lower bits of Dm that is supplied to the selection
circuit 144B. In the voltage applied period Tv, both the stop
timing signal Cs and the no-bias timing signal Cb is inactive,
which means that the image data Di is selected. In the brake
voltage applied period Ts, the stop timing signal is active, with
the result that the brake voltage data Dsi is selected. Besides, in
the no-bias period, the no-bias timing signal Cb is active, with
the result that the common voltage data Dcom.
[0175] The selected data in this way is supplied to the D/A
converter 145 in FIG. 23 and outputted to each data line 101 as the
data line signal from X1 to Xn.
[0176] (C-3) Operation of Electrophoretic Device
[0177] The operation of an electrophoretic display in this
embodiment is similar to that of the first embodiment described
referring to FIG. 8, in a point of its sequence that starts with
resetting, followed by writing, holding, and ends with rewriting.
However, it differs in having the process in which the brake
voltage is applied to the pixel electrodes 104 in writing (contains
rewriting). In the following, the difference, that is, details of
the writing operation will be described.
[0178] FIG. 26 shows a timing chart of the electrophoretic device
in the writing operation. Here is depicted about ith line and jth
column but it is obvious that other pixels can be, of course, dealt
likewise. In the next previous field, the pixel Pij has displayed
the gradation 100%. The voltage of the data line signal, which is
supplied to the jth data line 102, equals to the gradation voltage
Vij during the gradation voltage applied period Tv which starts
with T1 and ends with T2 as shown in FIG. 26. In the period of the
brake voltage applied period Ts from T2 to T3, it equals to the
brake voltage Vs, and in the no-bias period Tb from T3 to T4 it
equals to the common voltage Vcom.
[0179] The scanning line signal Yi which is supplied to the ith
scanning line 101 is active in the ith scanning line period. Hence
the TFT 103 which comprises the pixel Pij is turned on in this
period, so that the pixel electrode 104 imports the data signal Xj
of from T1 to T4. Namely, in this example, the operation which
starts with applying the gradation voltage Vij and ends with
applying voltage of the common voltage Vcom between the two
electrodes is completed.
[0180] In the following, the pigment praticles' motions will be
described in the pixel Pij. Having been done the reset operation
before the writing operation begins, at time Ti, all pigment
praticles of the pixel Pij are positioned on the side of the pixel
electrode 104. At this time when the voltage 104 Vij is applied to
the pixel electrode 104, an electric field is generated which is in
the direction of from the common electrode 201 from to the pixel
electrode 104. Thus pigment praticles 3 start to migrate at time T1
and the brightness Iij is being gradually high.
[0181] At time t2, the brake voltage Vs is applied to the pixel
electrodes 104. The value of the brake voltage Vs is set based on
the gradation voltage Vij which has been applied in the immediately
previous period and has negative-polarity with respect to the
common voltage Vcom. That is because the electric field to
counteract Coulomb force must be applied, which was applied to the
pigment praticles 3 in the direction of from the pixel electrodes
104 to the common electrode.
[0182] This brake voltage Vs, as it were, acts as a brake upon the
particles 3 to give them Coulomb force whose direction is opposite
with respect to their motions. With this operation the particles 3
stop moving until time T3 which is the end of the voltage applied
period Ts.
[0183] At time T3, the common voltage is applied to the pixel
electrodes 104. The voltage of the pixel electrodes 104 coincides
with that of the common electrode 201 to take away the charge
accumulated in the electrodes. By doing so, any electric field
isn't generated any longer and thus the positions of the pigment
praticles 3 can be held.
[0184] In the writing operation of this embodiment, firstly the
pigment praticles 3 migrate by applying the gradation voltage Vij,
then the particles 3 brake to stop by applying the brake voltage
Vs. Therefore even if the viscous drag of the dispersion medium 2
is small, a distance which the pigment praticles 3 migrate until
the particles 3 stop due to their inertia can be short. This
enables to display stable images in a short time without
fluctuation of brightness.
[0185] (D) Fourth Embodiment
[0186] In the third embodiment, the gradation voltage is applied.
It is also possible to apply the differential voltage.
[0187] FIG. 27 shows a block diagram of the image signal processing
circuit 301B.
[0188] A brake voltage generation part 350 has a table in which the
brake voltage data Ds' and a differential image data Dd whose
values are correspondent to those of Ds' are memorized. This means
that the brake voltage data Dds is to be acquired by accessing the
table and pointing to the differential image data Dd as the
address. The table is configured with storage circuits such as RAMs
and ROMs.
[0189] The brake voltage data Dds corresponds to the brake voltage
Vds, which will be described later, and is used for braking the
pigment particle 3. As mentioned above, particles 3 continue moving
due to their inertia even if the electric field is not applied to
dispersal system 1 any longer. But force moving in the opposite
direction enables braking and stopping particles 3. Since the
pigment particles 3 are moving according to the gradation voltage
when the image is going to displayed, it is necessary to apply an
electric field whose direction is opposite and, furthermore, whose
intensity is dependent on the kinetic energy of particles 3, in
other words, the differential voltage Vd. Therefore, in this
embodiment, taking the fluid resistance of the dispersion medium 2
and some other effects into consideration, the brake voltage data
Dds corresponding to the values of the differential image data Dd
is memorized in the table beforehand and is to be read the table as
required.
[0190] The data line drive circuit and the selection circuit are
similar to those of the second embodiment, therefore explanation is
omitted here.
[0191] (D-1) Operation of the Electrophoretic Device
[0192] FIG. 28 shows a timing chart of the electrophoretic display
in the writing operation. An ith line (ith scanning line) and a jth
column (jth data line) are depicted but it is obvious that other
pixels can bedealt with similarly In the following, the pixel of
the ith line and the jth column is represented by Pij, the
differential voltage to be displayed in the pixel Pij is
represented by Vdij and the brightness of Pij is represented by
Iij. Suppose the gradation in Pij was 10% in the next previous
period.
[0193] A voltage of the jth line signal Xj, which is supplied to
the jth data line 102, as shown in FIG. 28, is equal to the
differential voltage Vdij in the differential voltage applied
period Tdv from time T1 to time T2. Provided that the gradation to
be displayed in the present field is 50%, the value of the
differential voltage Vdij is -V50 indicated as the solid line
therein, because the voltage decreases by 50% from the previous
one. By another way of example, if the gradation to be displayed in
the present field is 0%, the value of the Vdij is -V100 indicated
as the dotted line therein. In the brake voltage applied period Ts
from time T2 to time T3, the voltage of the data line signal Xj is
equals to the brake voltage Vdsij. The value of the brake voltage
Vdsij corresponds to that of Vdij. In the no-bias period from time
T3 to time T4, the voltage of the data line signal is equal to the
common voltage Vcom.
[0194] (E) Fifth Embodiment
[0195] (E-1) Display
[0196] In the electrophoretic device of the first embodiment, the
gradation voltage applied period Tv and no-bias period Tb are set
in the period of one horizontal scanning. Motions of the pigment
particles finish within the period.
[0197] Instead, in the electrophoretic devices of the fifth
embodiment, a gradation voltage applied period and a no-bias period
are set on a field-to field basis. A configuration of this
electrophoretic device is similar to that of the first embodiment
as shown in FIG. 3, except for the period in which the no-bias
signal timing Cb is active.
[0198] (E-2) Whole Operation
[0199] FIG. 29 shows a timing chart of the whole operation in the
electrophoretic display. As shown therein, the image signal
processing circuit 300A outputs the reset data Drest in the reset
period Tr. In this period, pigment particles 3 are attracted to
pixel electrodes 104 so that their positions are initialized.
[0200] Next, a writing period is composed, of the gradation voltage
applied period Tvf and the no-bias period Tbf on a field-to-field
basis. In the gradation voltage applied period Tvf, the gradation
voltage is applied to pixel electrodes 104 based upon outputted
image data D outputted from image signal processing circuit 300A.
But the no-bias signal Cb remains inactive in that period hence the
common voltage Vcom is not applied to pixel electrodes 104.
[0201] While in the no-bias period Tbf, the image signal processing
circuit 300A does not supply any data but the no-bias timing signal
Cb becomes active, so that the common voltage Vcom is applied to
all data lines 102.
[0202] Therefore, the common voltage Vcom is applied to each of
pixel electrodes 104. That is, in this embodiment, the gradation
voltage D is applied in a certain period of a certain scanning
line, then gradation voltage V is maintained until the scanning
line is again selected, then the common voltage Vcom is applied to
pixel electrodes 104 in the next period in which the scanning line
is selected.
[0203] In the holding period Th, there is no electric field between
the pixel electrodes 104 and the common electrode 201, thus
enabling holding the image displayed in the previous writing
period.
[0204] In the rewriting period, as in the displaying of the first
period, a series of the processing which entails resetting,
applying the gradations voltage, applying the common voltage
(no-bias), and so on is carried out.
[0205] (E-3) Writing Operation
[0206] FIG. 30 is a timing chart of the electrophoretic display in
the writing operation. Pij which is on ith line and jth column is
depicted, but it is obvious that other pixels can be described
similarly. The voltage of the data line signal Xj which is supplied
to the jth data line 102 varies by the scanning line period in the
gradation voltage applied period Tvf as shown in FIG. 30. In the
period of the ith scanning line, the data line signal Xj is equal
to the gradation voltage Vij. At this time, since the scanning line
signal Yi becomes active (the H-level), the gradation voltage Vij
is applied to pixel electrode 104, thereby, at time T1, shifting
the voltage of pixel electrode 104 from the reset voltage Vrest to
the gradation voltage Vij so that the electric field corresponding
to the gradation to be displayed is applied to the dispersal system
1.
[0207] At time T2, when the scanning line signal Yi becomes
inactive (the L-level), the TFT 103 of the pixel Pij shifts to OFF.
However since some charge is accumulated in the capacitor, the
voltage of the pixel electrode 104 remains the gradation voltage
Vij.
[0208] In the period of the ith horizontal scanning in the no-bias
period Tbf, when the scanning signal Yi becomes active, the common
voltage Vcom is applied to pixel electrode 104. Therefore the
voltage of pixel electrode 104 coincides with the common voltage
Vcom at time T4.
[0209] (E-4) Motions of the Pigment Particles
[0210] Having completed the resetting operation before starting the
writing operation, at time TO, the pigment particles 3 are all
positioned on the side of pixels 104. At time T1, when the
gradation voltage Vij is applied to pixel electrodes 104, an
electric field is applied in a direction from pixel electrodes 104
to the common electrode 201. Hence the pigment particles 3 start to
move, increasing the brightness Iij.
[0211] The electric field corresponding to the gradation voltage
Vij is applied over one scanning field from time T1 to time T4.
Hence, during this period, the pigment particles 3 continue moving
to pixel electrodes 104. Namely, in the first embodiment, the
gradation voltage Vij is applied in a certain period within one
horizontal scanning, while in the fifth embodiment the gradation
voltage is applied over a period of one scanning field. The amount
of motion of the pigment particles 3 is, as explained above,
dependent on the electric field applied to the dispersal system and
the duration thereof. In this embodiment, since the electric field
is applied over one scanning field for a long time, even a weak
electric field can attain the brightness Iij desired. Therefore it
is possible to drive the data lines signal from X1 to Xn using low
voltage based upon this embodiment.
[0212] (F) Sixth Embodiment
[0213] In this embodiment, it is possible to apply differential
voltages to obtain desired gradations of an image displayed.
[0214] FIG. 31 is a timing chart showing the entire operation
utilized in operating the electrophoretic display. As shown therin,
the image signal processing circuit 301A outputs the reset data
Drest in the reset period Tr. In this period the pigment particles
3 are attracted to the pixel electrodes 104 to enable their
positions to be initialized.
[0215] The writing period Tw comprises a plurality of unit periods,
consisting of a pair of applied period differential voltages Tdvf
and no-bias period Tdbf. In gradation voltage applied period Tdvf,
the gradation voltage is applied to the pixel electrodes 104 based
on the image data D outputted from the image signal processing
circuit 300A. The no-bias signal Cb remains inactive in this period
and therefore the common voltage Vcom is not applied to the pixel
electrodes 104.
[0216] However, in the no-bias period Tdbf, the image signal
processing circuit 300A supplies no data but the no-bias timing
signal Cb becomes active, whereby the common voltage Vcom is
applied to all of data lines 102.
[0217] As a result, the common voltage Vcom is applied to each of
pixel electrodes 104. That is, in this embodiment, the gradation
voltage D is applied within a particular scanning line period, and
the differential voltage Vd is maintained until a scanned line is
again selected. After this, a common voltage Vcom is applied to the
pixel electrodes 104 in a period in which the scanning line is
selected next.
[0218] In the holding period Th, there is no electrostatic field
between the pixel electrodes 104 and the common electrode 201,
which enables to hold the image displayed in the next previous
writing period.
[0219] (F-2) Writing Operation
[0220] FIG. 32 is a timing chart of the electrophoretic display
showing a writing operation. Depicted is Pij, located on an ith
line and jth column, but it is will be apparent to those skilled in
the art that other pixels can be described likewise. Provided that
the gradation of the pixel Pij in the previous unit period is 10%
and that in the present unit period is 50%.
[0221] The voltage of the data line signal Xj which is supplied to
the jth data line 102 varies as a result of the scanning line
period in the differential voltage applied period Tdvf as shown in
FIG. 32. In the period of the ith scanning line, the data line
signal Xj is equal to the differential voltage Vdij. At this time,
since the scanning line signal Yi becomes active (the H-level) the
differential voltage Vdij is applied to the pixel electrode 104.
Thereby, at time T1, the voltage of the pixel electrode 104 shifts
from the reset voltage Vrest to the differential voltage Vdij, with
the result that the electrostatic field corresponding to the
display gradation to be displayed is applied to the dispersal
system 1.
[0222] At time T2, when the scanning line signal Yi becomes
inactive (the L-level), the TFT 103 of the pixel Pij shifts to OFF.
However, since some charge is accumulated in the capacitor, the
voltage of the pixel electrode 104 remains subject to differential
voltages Vdij.
[0223] In the period of the ith horizontal scanning in the no-bias
period Tdbf, when the scanning signal Yi becomes active, the common
voltage Vcom is applied to the pixel electrode 104. Therefore the
voltage of the piexel electrode 104 coincides with a common voltage
Vcom at time T4.
[0224] (G) Seventh Embodiment
[0225] (G-1) Display x
[0226] In the electrophoretic device described in the second
embodiment, the gradation voltage applied period Tv, the brake
voltage applied period Ts, and the no-bias period Tb are set to
constitute a period of one horizontal scanning to migrate and brake
the pigment particles 3.
[0227] Differently, in the seventh embodiment, a gradation voltage
applied period Tvf, the voltage applied period Tsf, and the no-bias
period are set on a field-to-field basis.
[0228] The configuration of this electrophoretic device is similar
to that of the third embodiment as shown in FIG. 3, except for the
period in which the no-bias signal timing Cb is active.
[0229] (G-2) Whole Operation
[0230] FIG. 33 shows a timing chart of the whole operation in the
electrophoretic display. As shown therein, the image signal
processing circuit 301A output the reset data Drest in the reset
period Tr. In this period the pigment particles 3 are attracted to
the pixel electrodes 104 and their positions are initialized.
[0231] The writing period is composed, on a field-to-field basis,
of the gradation voltage applied period Tvf, the brake voltage
applied period Tsf and the no-bias period Tbf. In the gradation
voltage applied period Tvf and the brake voltage applied period,
the gradation voltage V and the brake voltage Vs are applied to the
pixel electrodes 104 based on the outputted image data D and the
brake voltage data Ds outputted from the image signal processing
circuit 301A. However, since no-bias signal Cb remains inactive in
this period, the common voltage Vcom is not applied to pixel
electrodes 104.
[0232] While in the no-bias period Tbf, the image signal processing
circuit 300A supplies no data, the no-bias timing signal Cb becomes
active, whereby the common voltage Vcom is applied to all data
lines 102. Therefore common voltage Vcom is applied to each of
pixel electrodes 104. That is, in this embodiment, the gradation
voltage V is applied within a certain period during which line
scanning is performed, and subsequently a gradation voltage V is
maintained until the scanning line is again selected; after which
brake voltage Vs is applied to pixel electrodes 104. Subsequently,
brake voltage V is maintained until the scanning line is again
selected again, after which common voltage Vcom is applied to pixel
electrodes 104 in a period during which the scanning line is
selected next.
[0233] In the holding period Th, no electrostatic field exists
between the pixel electrodes 104 and the common electrode 201,
thereby enabling an image displayed to be held until the next
writing period commences.
[0234] In the rewriting period, as in displaying of the first
period, the series of the processing which contains resetting,
applying a gradation voltage, applying a brake voltage, applying a
common voltage (no-bias), and so on is carried out.
[0235] (G-3) Writing Operation
[0236] FIG. 34 is timing chart of the electrophoretic display in a
writing operation. Here will be described Pij which is on ith line
and jth column, but it will be apparent that other pixels can be
described likewise. The voltage of the data line signal Xj which is
supplied to the jth dsta line 102 varies within the scanning line
period of the gradation voltage applied period Tvf as shown in FIG.
34. In the period of the ith scanning line, the data line signal Xj
is equal to the gradation voltage Vij. At this time, since the
scanning line signal Yi becomes active (the H-level) the gradation
voltage Vij is applied to the pixel electrode 104. Thereby, at time
T1, the voltage of the pixel electrode 104 shifts from a reset
voltage Vrest to a gradation voltage Vij so that the electrostatic
field according to the gradation to be displayed is applied to the
dispersal system 1.
[0237] At time T2, when the scanning line signal Yi becomes
inactive (the L-level), the TFT 103 of the pixel Pij shifts to OFF.
However since some charge is accumulated in the capacitor, the
voltage of the pixel electrode 104 remains the gradation voltages
Vij. See previous.
[0238] In the period of the ith horizontal scanning of the brake
voltage applied period Tsf, when the scanning signal Yi becomes
active, the brake voltage Vsij according to the gradation voltage
Vij is applied to the pixel electrode 104. Hence the voltage of the
pixel electrode 104 is equal to that of the brake voltage.
[0239] In another period of the ith horizontal scanning in the
no-bias period Tbf, when the scanning signal Yi becomes active, the
common voltage Vcom is applied to the pixel electrode 104.
Therefore the voltage of the pixel electrode 104 coincides with the
common voltage Vcom at time T4.
[0240] (G-4) Motions of Pigment Particles
[0241] Having completed the resetting operation before the writing
operation starts, at time T0, the pigment particles 3 are
positioned at the side of the pixels 104. At time T1, when the
gradation voltage Vij is applied to the pixel electrodes 104, an
electrostatic field is applied in the direction of from the pixel
electrodes 104 to the common electrode 201. Hence the pigment
particles 3 start to migrate, increasing brightness Iij.
[0242] In one horizontal scanning period of from T4 to T6, the
brake voltage Vsij is applied between the two electrodes. Since the
brake voltage Vsij is negative relative to the common voltage Vcom,
Coulomb force act in the direction of from the common electrode 201
to the pixel electrode 104, which is opposite to that of motions of
the particles 3. This causes the particles 3 to lose velocity and
become stationary by time T6. Additionally, in a period of from
time T6 to time T7, a common voltage Vcom is applied to the pixel
electrodes 104, thereby removing a charge accumulated between the
electrodes. As a result, after time T7, ino electrostatic field is
applied by even though TFT 103 is turned OFF. Consequently, the
positions of the pigment particles 3 are set.
[0243] In the third embodiment, the gradation voltage Vij, the
brake voltage Vs, and the common voltage Vcom are applied within a
defined period constituting one horizontal scanning; while in the
seventh embodiment the gradation voltage Vij and the brake voltage
Vsij are applied over a single scanning field period. In this
embodiment, since the electrostatic field is applied over the
entire period of a scanning field period, even a weak electrostatic
field can attain a brightness Iij desired. Consequently, in this
embodiment it is possible to drive the data lines signal from X1 to
Xn, using a low voltage.
[0244] (H) Eighth Embodiment
[0245] In the seventh embodiment, the gradation voltage is applied.
However, it is also possible to apply a differential voltage.
[0246] (H-1) Operation
[0247] FIG. 35 is a timing chart of the whole operation in the
electrophoretic display. As shown, the image signal processing
circuit 301B outputs the reset data Drest in the reset period Tr.
In this period, the pigment particles 3 are attracted to the pixel
electrodes 104 and their positions are initialized.
[0248] The writing period is composed, on a field-to-field basis,
of the gradation voltage applied period Tdvf, the brake voltage
applied period Tdsf and the no-bias period Tdbf. In the
differential voltage applied period Tdvf and the brake voltage
applied period, the differential voltage Vd and brake voltage Vds
are applied to the pixel electrodes 104 based upon the outputted
image data D and the brake voltage data Ds outputted from the image
signal processing circuit 301B. But the no-bias signal Cb remains
inactive in that period hence the common voltage Vcom is not
applied to the pixel electrodes 104.
[0249] While in the no-bias period Tdbf, the image signal
processing circuit 300A does not supply any data but the no-bias
timing signal Cb becomes active, so that the common voltage Vcom is
applied to all the data lines 102.
[0250] Therefore the common voltage Vcom is applied to each of the
pixel electrodes 104. That is, in this embodiment, the differential
voltage Vd is applied in a preset period in which a particular
scanning line is selected, with the differential voltage Vd being
maintained during a next and different period in which the scanning
line is again selected, after which the brake voltage Vds is
applied to the pixel electrodes 104 during a subsequent and
different period in which the scanning line is again selected, the
brake voltage Vds then being maintained until the scanning line is
once more selected in a next and different period, after wihich the
common voltage Vcom is then applied to the pixel electrodes 104 in
a next and different period in which the scanning line is once
again selected. In the holding period Th, no electrostatic field
exists between the pixel electrodes 104 and the common electrode
201, and thus image displayed in either a next or previous writing
period can be held.
[0251] In the rewriting period, as in a first time display,
processing which is carried out consists of applying a reset
voltage, applying a gradient voltage, applying a brake voltage, and
applying a common voltage (no-bias).
[0252] (G-3) Writing Operation
[0253] FIG. 36 is timing chart of the electrophoretic display in
the writing operation. Here will be depicted about the pixel Pij
which is on ith line and jth column, but it is obvious that other
pixels can be described likewise. Suppose a gradation of the pixel
Pij in the next previous unit period is 10% and that in the present
unit period is 50%, for instance.
[0254] The voltage of the data line signal Xj, which is supplied to
the jth data line 102, equals to the differential voltage Vdij in
the ith horizontal scanning in the differential voltage applied
period Tdvf as shown in FIG. 36. At this time, since the scanning
line signal Yi becomes active (the H-level), the differential
voltage Vdij is applied to the pixel electrode 104. Thereby, at
time T1, the voltage of the pixel electrode 104 shifts from the
reset voltage Vrest to the differential voltage Vdij so that the
electrostatic field according to the gradation to be displayed is
applied to the dispersal system 1.
[0255] At time T2, when the scanning line signal Yi becomes
inactive (the L-level), the TFT 103 of the pixel Pij shifts to OFF.
However, since some charge is accumulated in the capacitor, the
voltage of the pixel electrode 104 remains in the form of the
differential voltages Vdij.
[0256] In the period of the ith horizontal scanning of the brake
voltage applied period Tdsf, when the scanning signal Yi becomes
active, the brake voltage Vdsij according to the differential
voltage Vdij is applied to the pixel electrode 104. Hence the
voltage of the pixel electrode 104 is equal to that of the brake
voltage.
[0257] In another period of the ith horizontal scanning in the
no-bias period Tdbf, when the scanning signal Yi becomes active,
the common voltage Vcom is applied to the pixel electrode 104.
Therefore the voltage of the pixel electrode 104 coincides with the
common voltage Vcom at time T4.
[0258] (I) Applications
[0259] So far, several embodiments have been described, However, it
is to be understood by those skilled in the art that this invention
is not restricted in these embodiments, and various applications
and variations are possible.
[0260] Following are some variations.
[0261] (I-1) Displaying of Animation
[0262] In the above embodiments, the process of displaying an image
consists of first resetting then writing, subsequently holding, and
then rewriting if necessary.
[0263] As a result, the electrophoretic displays in those
embodiments are suitable for displaying a static image. However it
is possible to display an animation by making the reset period Tr
as well as by repeating rewriting periodically. In displaying an
animation, it is preferable that the velocity of the pigment
particles 3 should be high. This means that small fluid resistance
is more suitable. In such a situation, the pigment particles 3 are
likely to continue to move due to their inertia after removal of
the electrostatic field. Therefore it is preferable to brake the
particles 3 by applying the brake voltage as described above.
[0264] (I-2) Refreshing
[0265] It is preferable that the specific gravity of the dielectric
fluid2 and that of the pigment particles 3 which comprise the
dispersal system 1 be equal. However, it is difficult to achieve
complete parity of the respective specific gravities, due to
restrictions of materials employed and variations therein. In such
a case, when the dispersal system 1 is left in stasis for a long
time once an image is displayed, the pigment particles 3 sink down
or float up due to gravitational effect. In order to overcome this
problem, it is preferable for a timer apparatus to be set in the
timing generator 400 to rewrite the same image for a certain
period. The timer apparatus 410 has a timer part 411 and a
comparison part 412. The timer generates duration data Dt measuring
time, in which the value of the duration data Dt is reset to `0`
when either a writing start signal Ws which designates an ordinary
writing, or a rewriting signal Ws' becomes active. The comparison
part 412 compares the duration data Dt with the predetermined
reference time data Dref which designates the refresh period and,
if they coincide, generates the rewriting signal Ws' which is
active during a preset period.
[0266] FIG. 38 is a timing chart of the timer apparatus 410. As
shown, when the writing signal Ws becomes active, the duration data
Dt of the timing part 411 is reset and measurement starts. When
predetermined refresh period has passed, the duration data Dt and
the reference time data Dref coincides, so that the rewriting
signal Ws' becomes active. The measurement of refreshing period
starts when the writing signal Ws becomes active, or the rewriting
signal Ws' is active once the refresh period passes.
[0267] By executing the rewriting operation (but the same image)
described in the above embodiments, by using the rewriting signal
Ws' which is generated to function as a trigger, a displayed image
is refreshed.
[0268] (1-3) Electronic Devices
[0269] Electronic devices attached to the electrophoretic display
described above are described as follows:
[0270] (1) Electronic Books
[0271] FIG. 39 is a perspective view showing an electronic book.
This electronic book 1000 is provided with an electrophoretic
display panel 1001, a power switch 1002, a first button 1003, a
second button 1004, and a CD-ROM slot 1005, as shown.
[0272] When a user activates the power switch 1002 and then loads a
CD-ROM in the CD-ROM drive 1005, contents of the CD-ROM are read
out and their menus displayed on the electrophoretic display panel
1001. If the user operates the first and second buttons 1003 and
1004 to select a desired book, the first page of the selected book
is displayed on the panel 1001. To scroll down pages, the second
button 1004 is pressed, and to scroll up pages, the first button
1003 is pressed.
[0273] In this electronic book 1000, if a page of the book is once
displayed on the panel screen, the displayed screen will be updated
only when the first or second button 1003 or 1004 is pressed. This
is because, as stated previously, the pigment particles 3 will
migrate only in when an electrostatic field is applied. In other
words, to hold the same screen display, it is unnecessary to
reapply any voltage. Only during a period for updating displayed
images, is it necessary to feed power to the driving circuits to
drive the electrophoretic display panel 1001. Thus, in comparison
to liquid crystal displays, power consumption is greatly
reduced.
[0274] Further, images are displayed on the panel 1001 by way of
the pigment particles 3 thus preventing any impression of
artificial brightness, and providing display characteristics in the
electronic book 1000 which are close to those provided or in
printed matter. This proximity of display characteristics of the
electronic book to printed matter limits eyestrain and makes it
possible for the electronic book to be read for extended periods of
time.
[0275] (2) Personal Computer
[0276] A portable, note-book typecomputer in which the
electrophoretic display is applied will now be exemplified. FIG. 40
is an external perspective view showing such a computer. As shown,
the computer 1200 has a main unit 1204 on which a keyboard 1202 is
mounted and an electrophoretic display panel 1206. On the panel
1206, images are displayed via pigment particles 3. Hence, it is
unnecessary to mount a back light, which is required in
transmission type and semi-transmission type of liquid crystal
displays, thereby imparting to the computer 1200 a lower weight and
smaller size, in addition to greatly decreased power
consumption.
[0277] (3) Mobile Phone
[0278] A mobile phone into which is incorporated the
electrophoretic display panel will now be exemplified. FIG. 4 1 is
a an external perspective view of a portable phone. As shown, a
portable phone 1300 is provided with a plurality of operation
buttons 1302, an ear piece 1304, a mouth piece 1306, and an
electrophoretic display panel 1308.
[0279] In liquid crystal displays, a polarizing plate is a
requisite component for enabling a display screen to be darkened.
In the electrophoretic display panel 1308, however, a polarizing
plate is not required. Hence the portable phone 1300 is equipped
with a bright and readily viewable screen.
[0280] Electronic devices other than those shown in FIGS. 39 to 41
include a TV monitor, outdoor advertising board, traffic sign,
view-finder type or monitor-direct-viewing type display of a vidoe
tape recorder, car navigation device, pager, electronic note pad,
electronic calculator, word processor, work station, TV telephone,
POS terminal, devices having a touch panel, and others. Thus, the
electrophoretic display panel according to each of the foregoing
embodiments can be applied for use with such devices.
Alternatively, an electro-optical apparatuses having such
electrophoretic display panel can also be applied to such
devices.
* * * * *